Overview
Thymosin Alpha-1 (Tα1) is the synthetic version of an N-acetylated 28-residue peptide originally isolated from calf thymus. It has been a registered drug under the trade names Zadaxin / Thymalfasin in 30+ countries (Italy, China, several Latin American and Southeast Asian markets) since the 1990s — variously approved for chronic hepatitis B, chronic hepatitis C, as a sepsis adjunct in critically ill patients, and as a vaccine adjuvant in hemodialysis patients and the elderly. It is NOT FDA-approved in the United States; it sits in a gray compounding space here. Editorially, this entry must hold the line on the jurisdictional split: Tα1 has Tier 1 evidence for specific approved indications in approved markets, but the popular framing as a generic 'immune booster' for healthy adults sits at Tier 3.
Mechanism
Modulates T-cell maturation and activity (boosts CD4+ and CD8+ T-cell function), enhances NK cell activity, increases dendritic-cell IL-12 and Th1 cytokine production, and shifts the cytokine milieu toward a Th1-dominant antiviral/antitumor pattern. Acts via TLR-9 and TLR-2 signaling on dendritic cells and through pleiotropic effects on T-cell receptor signaling. Does not directly kill virus or tumor — its effect is to upregulate host immune competence, which is why most evidence comes from contexts of immune compromise (HBV/HCV chronicity, sepsis, chemotherapy).
Evidence by indication
We classify each indication separately. The same peptide can be Tier 1 for one use and Tier 4 for another. Tiers reflect the published literature, not the strength of community framing.
Chronic hepatitis B (in approved markets)
Multiple controlled trials and meta-analyses (notably across Italian and Chinese cohorts) demonstrate sustained virological response and ALT normalization, sometimes combined with interferon. Approved indication in Italy, China, and other jurisdictions. Tier 1 for THIS specific indication in THESE jurisdictions; tier does not propagate to other claims.
Sepsis adjunct (in critically ill patients)
ETASS RCT (Wu et al., Crit Care 2013, n=361) and follow-up Chinese trials reported reduced 28-day mortality in severe sepsis. The recent TESTS / ETASS-II readouts have been mixed. Tier 2 because effect size and replication are not yet uniformly positive across populations.
Vaccine adjuvant (immunocompromised / dialysis / elderly)
Trials in hemodialysis patients receiving hepatitis B vaccine and in elderly receiving influenza vaccine showed improved seroconversion. Modest effect sizes and limited replication in modern settings.
General 'immune support' in healthy adults
Wellness-clinic and community use is overwhelmingly in healthy adults seeking generic immune optimization or post-COVID recovery. There is no controlled trial of Tα1 in healthy adults for prevention or generic immunity. Mechanism is plausible; the indication-specific evidence is absent.
No primary citations are anchored to this indication — the tier reflects the absence of usable literature, not a missing reference.
Cancer / chemotherapy adjunct
Several adjunctive-use trials in melanoma, hepatocellular carcinoma, and non-small-cell lung cancer have explored Tα1 alongside chemotherapy or interferon. Results are heterogeneous; no single landmark RCT establishes a reliable survival benefit. Tier 2 with caution.
Studied dose ranges
The ranges below come from published trial protocols where available, and from documented self-experimenter consensus where the literature does not include human dose-finding work. The notes flag which is which.
Approved-market chronic hep B/C dosing is typically 1.6 mg SubQ twice weekly for 6–12 months. Note unit math: 1.6 mg = 1,600 mcg.
Sepsis-adjunct ICU dosing has used 1.6 mg SubQ q12h for 5–7 days in published trials.
Contraindications
- Solid organ transplant recipients on immunosuppression (theoretical risk of accelerating rejection; consult transplant team)
- Active autoimmune disease (e.g., uncontrolled lupus, severe RA) — immunostimulant could worsen flares
- Known hypersensitivity to Tα1 or formulation excipients
- Pregnancy and breastfeeding (limited human safety data outside specific trial populations)
Reported side effects
- Injection-site discomfort, transient erythema
- Mild flu-like symptoms (less common than with interferon)
- Transient lymphocytosis or eosinophilia
- Rare: rash, pruritus
- Generally favorable safety profile across decades of use in approved markets
Reconstitution & storage
Lyophilized powder reconstituted with the supplied diluent (typically 1.6 mg vial reconstituted to 1 mL = 1.6 mg/mL). A standard 1.6 mg dose is the full mL. Compounded US-market vials may differ in concentration — verify per batch.
Storage. Lyophilized: refrigerate 2–8 °C per label. Reconstituted: refrigerate; use promptly per vendor expiration (commonly 24 hours for the licensed product, longer for compounded BAC-water reconstitution).
Open the peptide calculator → to compute exact draw volumes for your specific vial and BAC water choice.
Editorial note
DRAFT — pending Wayne's review. The editorial gravity here is the jurisdictional split: Tα1 has decades of approved use abroad and credible Tier 1/2 evidence for hepatitis indications and sepsis, but US wellness-clinic users are buying it for 'general immune support,' which sits firmly at Tier 3. Don't let the hepatitis-B tier propagate. Per Skill rule 6, FDA approval (and by extension regulator approval generally) does not propagate across indications.
Citations
- [1]Thymosin alpha 1 therapy in chronic hepatitis B: a systematic review and meta-analysisYang Y, Xu X, Wang Y, et al. · Antiviral Therapy · 2010 · PMID 20167030Tier 1 anchor for chronic hepatitis B indication in approved jurisdictions.View source
- [2]The efficacy of thymosin alpha 1 for severe sepsis (ETASS): a multicenter, single-blind, randomized and controlled trialWu J, Zhou L, Liu J, et al. · Critical Care · 2013 · PMID 23394259Anchor Tier 2 RCT for the sepsis-adjunct indication; reduced 28-day mortality in severe sepsis.View source
- [3]Historical review of thymosin α1 in infectious diseasesCamerini R, Garaci E. · Expert Opinion on Biological Therapy · 2015 · PMID 29224537Cross-indication review supporting hep C, vaccine adjuvant, and oncology use claims.View source